Fix FROM

Author: luigidellaquila

x-pack/plugin/esql/src/main/antlr/lexer/From.g4

@@ -23,6 +23,9 @@ FROM_COMMA : COMMA -> type(COMMA);
 FROM_ASSIGN : ASSIGN -> type(ASSIGN);
 METADATA : 'metadata';
 
+// we need this for EXPLAIN
+FROM_RP : RP -> type(RP), popMode;
+
 // in 8.14 ` were not allowed
 // this has been relaxed in 8.15 since " is used for quoting
 fragment UNQUOTED_SOURCE_PART